Lakshya NEET in English 2027 Solutions 🧪 Class 12 Backlogs Class

Added: 2026-06-01

[00:00:06]Good evening. Good evening.

[00:00:09]Good evening, neat warriors.

[00:00:13]I hope I'm clearly visible and audible.

[00:00:18]Yes, now I can see myself.

[00:00:21]Now I can see myself. So I hope I'm clearly visible and audible everybody.

[00:00:27]So let's see uh on this 30th May who have joined us for Laksh neat in English backlog series because today I am going to start and finish solution chapters beta the chapter for solution in collleative properties is not uh okay.

[00:00:50]So good evening. I hope I am clearly visible and audible beta. Just let me give just uh somebody please give me that confirmation.

[00:01:03]I know I am but uh I'm just checking the level of participation from you people.

[00:01:09]So Surya is asking if anyone from Karnataka. Surya is very much interested in Karnataka students from his side.

[00:01:21]Okay. Chaloba. So am I Shubhham? Are you Surya? Am I clearly visible and audible everybody? Okay. So what's up? I'm good.

[00:01:32]So Adasha now let's start. Uh the task for today uh the task for today is we have to start and finish a very important yet very crucial yet very easy why I'm saying easy beta it will be a highcoring chapter for all you neat warriors out there you know why first the the type of question that comes from solution chapter in your neat examination is is always very specific and particular. They either ask you about collleative properties. There are four collleative properties. Now what are they? For them you have to understand what is a solution. And in order to calculate those collleative properties you need to understand how to how to know and how to calculate the concentration terms of a solution. So if you learn concentration terms then this will also help you in your class 11th mole concept. So actually learning this chapter will help you at least make one to two questions correct from mole concept and obviously this chapter independently gives you two sometimes three questions. So rather it becomes a five question journey. So that's why this first chapter of of of solution and collleative property is that's why very crucial. Sir is the session worthy for revision purpose like questions are there in the session beta other we are definitely doing loads of u marathon sessions for the renate examination there we take too many questions there we take sufficient amount of questions so this session is for all the class 12 students who wish to join Laksh neit in English because obviously the anniversary offer from PW the sixth year anniversary offer are are is are is definitely happening and there are many students there are many students who are rushing into the batch of neat uh in English lux need in English so for those students uh so word solution chapter is done electrochemistry is halfway done so they need a they wanted a oneshot so that's why this is a backlog uh session for them and obviously if you also find interest and obviously the chapter will help you academically and obviously once you will join us inside the batch we'll be having more exposure towards it. So without any further delay let us start the chapter of solution and collleative properties. Now I hope uh everybody is beta acha one one thing we will be making it very precise because I do not want to waste your very valuable time so we'll be making it very precise so that uh you may also have a feeling that the chapter is actually worth it is quite doable also at the same time point point of time it is quite conceptual also so I am offline student okay okay Adash very good Cheers to that. But yes, definitely this online version will also help you to in that case if you have read this uh chapter then it will be helping you to have a thorough revision. Now uh the chapter of solution which uh now the point that I was making I just missed that because of that uh comment. uh now I what I'm saying is beta do not try to write these notes because all these lecture notes you can obviously access for free even if you're not uh planning to join Lux neat in English but still the chapter of solution and collleative properties you can uh read from here and you can directly download all these lecture notes from where just you have to join PW neat English WhatsApp channel and the moment I'll be finishing this live which is uh in another 1.5 in 5 hours and uh then you can download these notes from the WhatsApp channel and have a thorough revision. Okay. I am from Dubai. Okay.

[00:05:31]Mr. Far Garun. So, hello from Dubai. Uh I mean uh hello from India to Dubai.

[00:05:39]Chalo. Now let's start the process beta.

[00:05:41]Now what is a solution sir? Solution I guess this you know from your class 9th or 10th basic sir. Solution is a mixture of two or more components. But here you can see the word homogeneous that means obviously a solution can be heterogenous as well where the physical state of the components may be different but we for J for mains for neat for for your class 12 board examinations as well we are I'm sorry we are more interested in homogeneous solutions. So okay so people are mentioning their state that is good. Karnataka Kashmir cho I just finished Laksh J uh batch that's why I'm just uh out of that bread. So the coffee has definitely added a bit of uh courage in my voice and throat as well. So with that let us start again now.

[00:06:48]So in our chapter we are more interested in sir I am joined yak need 2027 Englishpad but no 2026 previous year lecture is present on kazana sir beta uh just put that thing in the in the uh comment section of the tech team uh in the PW app itself. you will be definitely getting updated with whatever resource uh has been uh notified and promised to you. But yes, sometimes there may be a system lag. So just report that in the uh in the the the student section there is a separate chat bot. You just uh put in your query and definitely the team will uh get back to you. H I hope I answered that uh future doctor Shri. Okay. Now so we are interested in these homogeneous solutions and what are these homogeneous solutions are homogeneous solutions are those where the component have uniform phase. If you mix a solid in a liquid after mixing it will get a same state and the state acquired by the solution defines that what is the solvent in that particular solution. Now if you mix two components then the solution is called binary solution and this is the solution from which we are given questions from J also both also. But yes obviously you can have more than uh two components. If three components are mixed then it is a t tertiary or turnary solution. If four components are mixed then it is a quarterary and so on and so forth. But we are interested in binary solutions because we are asked questions from binary solution. Now now okay. So someone is from Lakshin. So perfect beta. It is a perfect chance for you to revise. Now what is a solvent beta? If you mix two components then which component deserves to be called as a solvent? There are two definition. The first definition is as I've already communicated that that component is termed as solvent which defines the physical state of the system and which defines the physical state of the system as in the as in the the whole solution is your system and whatever component is defining the state of the state of the solution is termed as its sol is termed as solvent and obviously the other component is termed as solute.

[00:09:07]The other definition sometimes s if if the state of both the components are same then then obviously I guess you know this also that the component which is present in larger amount will be termed as solvent. Now on the basis of physical state the of the solvent and solute the types of solutions are as follows. Sir what are they primarily nomenclatured as? So if your solvent is a gas then the type of solution will be termed as a gaseous solution. The solute can be gas, liquid, solid, anything. If aa there is a printing error. So let me correct it. If the solvent is liquid then whatever may be the solute gas liquid or solid that will be termed as a liquid solution. And this is what we are interested in because we are asked questions from this area only. And obviously if the solvent is a solid.

[00:10:07]Hey sir, solvent can be solid. Yes.

[00:10:10]Because if you mix either a gas in a solid, a liquid in a solid or a solid in a solid, ultimately the mixture the solution is is is having a physical state which is solid state. That's why the solution will be termed as a solid solution. The examples are rather very important.

[00:10:28]Gas in solid solution. What is the famous example sir? Solution of hydrogen in paladium. If you must have observed that hydrogenation reaction.

[00:10:36]Hydrogenation those hydrogen gases and unsaturated hydrocarbon gases they are passed over solid catalytic surfaces and those catalytic surfaces after [clears throat] absorption of the gases as a as a mixture that again becomes a solid. So gases getting absorbed on the solid surface which which leads to the formation of the hydrogenation of those hydrocarbons which I guess you know from your class 9th and 10th and that you know from your class 9th and 10th. Uh okay what an accent sir beta try to okay thank you for the for the compliment regarding the accent but beta we are here to learn logic behind chemistry. So obviously I thank you beta. Thank you motivational content. Okay nice name.

[00:11:27]Now beta. So gas in solid solution liquid in solid solutions are give as an example. Amalgam are the famous example.

[00:11:35]Now we know mercury at room temperature is a liquid. So if the liquid mercury gets associated with let's say sodium a very famous alloy sodium amalgam then the solution is obviously a solid that means sodium is a solid but we are mixing liquid solute as in mercury into it. So the alloy is termed as amalgam where solute is liquid and solvent is solid. Last one solid and solid solution sir are alloys. So all the alloys that we have have a larger for example you buy a 18 karat gold chain that means it is having 18 part of gold and six part because out of 24 parts six part is of another solid solute which is making the gold workable which is why gold is having that your jewelries are having that shape because pure gold pure iron pure metals are generally not workable teaching with action and so clear English Okay. So, thank you again. Sor jen cho action I'm not doing any action beta aa. Okay.

[00:12:41]This is natural instinct my friends. Cho moving forward sir. If the solutions are I mean sir you can add any number of solute in any amount of solvent. So so com chemistry community have decided and defined certain concentration terms. So can you so that you can define the concentration of a solution because you can have any number of probabilities of mixing those solute in variable amount of solvents. So rather the community the science the chemistry community have defined.

[00:13:15]Okay. So the community Okay. Thank you. Thank you. Thank you.

[00:13:20]So the community have defined that we will be defining certain concentration terms for the solution. But for the case of our mathematical ease I'm telling you we will always mark solvent as one.

[00:13:33]Please make we as in GSS students you as my students will always remember this that whenever we'll be doing those calculations for concentration terms we whenever we are writing one you will mean that I am referring for solvent whenever I'm writing two you will mean I am referring for solute and whenever obviously solution is written but obviously I will not write the complete solution I will write solution like this okay now [gasps] the first concentration term sir is percentage composition uh this you In your Maggie packet, every 100 g contains this many gram, this gram of this many milligram of this, this milligram of sodium, this milligram of energy, whatever. So these concentration terms are definitely used for your Maggi and whatever product you buy per 100 g contain this many gram, this migron, this many gram whatever. Now you bi biology student we I am specifically I'm I am an engineer hardcore engineer. So obviously your bio people the biology uh your madam will be definitely telling you what are those ingredients. So for though for the percentage composition are generally used over there. Now how many types of percentage composition we have in our practical life we have mass by mass percent as in mass of solute upon mass of solution into 100 volume by volume percent. For your ruabza bottle, every 100 ml bottle contain this ml cost this much ml something. So volume by volume percentage is also used in many of the mixture. So this will be volume of solute upon volume of solution into 100. Then mass by volume which is mass of solute upon volume of solution. So denominator always signify solution. But here you can obviously mathematically see whatever unit I will you use in the numerator I will use the same unit in the denominator. That's why I have not mentioned unit over there. But you are not free. It is defined. So you need to learn this that whenever using mass by volume percentage, you have to write mass in gram and volume in ml and then multiply by 100 because sir we are defining these concentration terms. Huh?

[00:15:41]So Maggie masala and everything. I hope you got the first concentration term.

[00:15:45]Obviously sir for very dilute solutions the solvent if having very limited amount of solute also sometimes instigates us. So during that what we do rather instead of percentage we find parts per million or sometimes parts per billion 1 million is 10 lak rupees because we Indians I mean we are comfortable with lak crores so 1 million is 10 lakh rupees as in 10 raised to the^ 6. So everything else remains the same. Mass percent, volume percent and mass by volume percent. Please remember this whenever you are putting mass by volume.

[00:16:20]Mass is in gram and volume is always in ml. The denominator signifies for the solution as in total. The numerator signifies for solute because solute decides practically more or less generally solute decides what the property of a solution. I hope everybody is with me till here.

[00:16:42]Rahana. Oh, now people are socializing.

[00:16:44]Okay, I didn't read that comment. I didn't read that comment. Okay, moving forward. Now, now for binary solutions, you can obviously define mole fractions as well. The name signify mole fraction of solute will be equal to number of moles of solute upon total moles. Total moles will be solute plus solvent. Mole fraction of solvent will be number of moles of solvent upon total moles. If you add mole fraction of two components in a binary solution, it will always be one beta. Most of the student always miss this. Please remember that for a binary solution, summation of mole fraction of all the components is always unity. Obviously you can see that mathematically LCM is same. So n1 + n_sub_2 upon n1 + n2. Moving forward now a basic question. Mole fraction of NaCCl in the solution containing one mole of NaCCl. Sir that means number of moles of solute is one. Now solvent is 100 g. So what is mole? Number of moles of water sir weight of water upon molecular mass of water. So if you are supposed to calculate mole fraction of solute then it will be n_sub_2 upon n_sub_1 + n_sub_2. Now this is just mathematics that you have to do. Just do the division and once you do you will get option one as your right answer beta.

[00:18:03]But these questions are also coming in your paper. So what I'm doing sir n_sub_2 as in 1 upon 1 + this is 55.55.

[00:18:11]So you can obviously now into divide is a thing which you can only master once you practice more and more. I hope everybody's clear. Moving next. Now other concentration terms are like one of the very famous concentration term is strength of a solution. What is strength of a solution? Strength is defined as weight of solute upon volume of solution. So this is weight of solute in gram. You cannot put in any other unit.

[00:18:36]It is defined upon volume of solution and this volume has to be placed in liter. Sir what will be its unit? Its unit will be gram per liter. I hope every now instead of weight if you write number of moles of solute upon volume of solution in liters then this will give you marity which is represented as capital m. Now you can obviously write number of moles of solute how sir number of moles of solute is equal to weight of solute in gram upon molar mass of solute into now capital m I'm using for marity m_sub_1 for molar mass of solvent m_sub_2 for molar mass of solute okay because one two remember that thing now sometimes volume of the solution in question is given in ml then rather you put in ml but s in the definition it is in liter then divide by th00and that 1,000 will definitely come in the numerator. So this will give you the I hope everybody is clear. This will give you the formula of marity. What will be it? It its units are moles per liter.

[00:19:46]Similarly, if you are not taking volume in denominator rather you are more specific about the weight of solvent.

[00:19:54]Again you have to learn these definitions. Then it will give you the definition of molality which is rather represented by a small m symbol. So this is equal to number of moles of solute upon weight of solvent in kg. Again number of moles of number of moles of solute can be written as weight of solute in gram upon molar mass of solute into weight of solvent in gram. Then a th00and will converted into kg. So these are the definitions these are the formulas from which you get direct questions. So sir for that you we have to learn those formulas. So kindly do that. Now what will be unit? unit is called molal. This is lull. For marity sometimes it is written moler l a r. For marality is written molal or rather moles per kg rather moles per kg. Uh Shrih Har is asking poll class uh beta.

[00:20:52]Yes, we generally all the time even we had 500 question MCQ this afternoon. We definitely have those polls but beta because this class we have structured as a backlog class. So intentionally what I have done is you are just I mean there will be so many students of mine that I know will be definitely watching this in a recorded version. So I do not want to waste even your time and their time with the unnecessary polling because beta my intention with this backlog series is to teach you the complete chapter. I'm not here to ask questions out of it. But sir, how will we practice beta after learning the chapter go and attempt your questions and if you find any problem just the video is always going to be there in the live section of PW neat English. Just go to the comment section.

[00:21:42]Whatever doubts you'll be having, I'll be giving you some homework questions also over here. Attempt them and if you have any doubt, I will be again coming I guess on on the next uh with the next session again the backlog series over there. First I'll be discussing whatever doubts you'll be putting in the comment section and then I'll be continuing with the with the backlog series of the second chapter. Okay. I hope I am clear with the process that we are going to follow beta.

[00:22:09]Perfect. Right. Right Mr. Arson. Thank you beta ch. Now uh sir that means we have defined mality also mality as in small m but one very important point which need all competitive examination find interest is in the the usability.

[00:22:28]So one common sense says that if you change temperature volume change. So whatever concentration term that has volume factor in it they change with temperature.

[00:22:38]Then sir whatever concentration term that do not have volume factor rather they only have mass factor they will not change with temperature. No sir that means it is better to use them because for example if I paste a sticker in my sol in my concentration bottle in winter if summer comes or concentration will change because volume change with temperature but all those physical quantity will remain the same which has only mass factor in it because mass is negligibly changed with temperature. You can obviously see mality has no volume term. It has only mass and mass has negligible effect. Practically you can say mass is unchanged with change in temperature. But yes because I teach for J advance also. So I cannot say it point blank because yes that's why I said I have been uh uh sophisticated enough in saying that that mass has negligible effect with change in temperature. So practically no effect and that that's why molity is considered as a better concentration term than capital M which is marity. I hope you can see that from the written text as well. Moving forward now we get these type of questions directly rather do a J mains question.

[00:23:51]So neat is J means they are same. So let us attempt that. Now this many gram of aqua solution contain 18 g glucose that means sir this is weight of solution. So weight of solution is given out to be 518 g sir this is weight of solute weight of solute is 18 g. Who is solute?

[00:24:14]So solute is glucose. So molar mass of glucose although we know also but it is given.

[00:24:20]You have to calculate the molality as in small mir small m is equal to number of moles of solute which is weight of solute upon molar mass of solute into weight of solvent. H sir this is solution beta solution is solvent plus solute. Solution is 518. Solute is 18.

[00:24:39]So solvent will be the difference as in 500. But because this is gram so I have to divide a,000 in the numerator which will definitely this is just a simple maths now. So I guess yes if you solve this I guess [snorts] just check beta a is your answer. Yes adjan perfect adju we have got we have got participants. Hi Casper. Hi Ravi Anu Patala.

[00:25:16]Okay, I'm sorry if I misread your online name. Cho, moving forward. I'm great.

[00:25:23]Moving forward now. Sir, can marity change? Yes, mix solutions.

[00:25:29]Sir, I have this solution marity m1 volume v_sub_1. Sir, I have another solution marity m_sub_2 volume v_sub_2 and uh I have mixed them. Let's say I have mixed uh water also. This is just plain water volume V3. And I have mixed all these and formed a resultant solution. So you tell me what will be the marity of the resultant solution.

[00:25:55]Sir, it will the total marity will be the total marity will be total moles. So moles from water sir water is just a solvent. So no moles. Moles sir moles is equal to marity into volume. So n_sub_1 will be m_sub_1 v_sub_1 number of moles from this guy will be sir m_sub_2 v_sub_2 upon total volume will be sir v_sub_1 + v_sub_2 plus volume of water if added now let's say this was just concentration and this was just this was just water so sir moles is only coming from here so moles initial and moles final will also be equal if I was having only one solution and water let's say this is not there if only this is there then sir moles is definitely the same. So moles initial is m1 v1.

[00:26:42]Moles final is s marity I do not know because it has gone dilute. So marity is m upon total volume is v_sub1 plus v3.

[00:26:50]So whatever I mean the common sense remains the same. I hope everybody's clear guys whoever is reading and not socializing.

[00:26:59]H yes yes kitika is definitely answering.

[00:27:04]Perfect perfect. Moving next sir like these questions you get like calculate final marity when 65 ml of this much molar H2S04 is diluted to 100 ml sir solute will only be coming will be given by H2S04. So number of moles initial will be equal to number of moles final because H2S04 is only coming from H2S04 solution water is not giving any H2SO.

[00:27:27]So number of moles is equal to sir initial marity is 0.5 initial volume sir this is an ml so why bother that volume also I'll put in ml so mill will be will be getting cancelled so don't bother so [snorts] 65 is equal to now what is number of moles finals or final mality I do not know that final marity let's say it is m final now what is final volume it is diluted two that means I have added water I do not know how much of water what is the final volume two if It is saying read the preposition beta. So it is not adding 500. It is adding water. So that 65 becomes 500 sir. So that means that is the final volume. Yes beta. So I hope now this is just into divide. You can do and find the answer. Yes people are answering also. Perfecto. Yeah.

[00:28:13]Perfecto. You guys are huh? Yes beta.

[00:28:16]This is 0.065. Perfect by perfect. I was not expecting this much of participation. 0.065.

[00:28:25]CH moving next. So again beta a J mains question sir how we'll do it this is 600 ml of.1 molar HCl and this is 400 ml of.1 mar you have to find pH sir pH is ionic nothing beta because what will be h plus final h plus ion concentration sir final final final normality why I'm saying normality beta because h24 will give 2 h+ so sir what is normality you have not took beta For acids normality is nothing but marity into valency factor. So we'll just do that and we'll get our answer. So what will be final marity sir? Beta in the same way n_sub_1 v_sub_1 plus n_sub_2 v2 aa upon total volume. We are not adding any water. So sir just like this. Now what is normality? Sir you already told us normality is marity into valency factor.

[00:29:24]What is valency factor for acid? number of H+ that it gives sir for HCL marity is 10^ minus2 into 1 so why bother writing one because valency will be 1 into 600 ml but sir volume is in ml beta ml ml ml s mill will be millie will be getting cancelled so why bother writing that th00and because that is anyhow going to be cancelled but yes if not then you have to consider those those unit also in mind that's why I'm iterating again and again now or s2 force are marity stands minus 2 but valency factor will be two and uh volume is s 400 upon sir beta upon volume is 400 + 600 as in uh 1,000 now just into divide you have to do once you get h+ ion concentration let's say it will come out to be a so pH will be minus of log of a now tell us how to calculate log if you actually want to know it after the live is done. I have told you that I'm giving you questions also your uh your job will to calculate them properly. If not after the live is done go to the comment section comment because in the live obviously you can you can on but nobody can then introspect.

[00:30:41]So I personally do this when whatever lives I do, I always check the comment section because whatever serious students we may have, they communicate, they write all their queries and I religiously uh read them and accordingly I perform in my next classes. So how what more you want out of us will be depending upon you. Post the class, download the notes, revise them, practice questions with your pen and copy and if you are stuck anywhere, I will be definitely coming back with the proper relevant relevant uh query resolution. But yes, for that comment section has to be filled. Ch.

[00:31:26]Now sir, there are some very important uh conversions sir. Why they are important? Because beta in your neat examination you directly get question even J question and sir because we directly get question that means sir we will derive in the exam no why we will derive in the exam sir you need to save time no so therefore learn these important conclusions but sir I want to I am sir advanced type although I'm becoming a doctor but I'm advanced type I will not I will be deriving them and then obviously after derivation you will understand and then at least try to do the derivations But finally try to try to learn them. Make them as your gunshots. So that whenever ne is throwing shooting you with any such questions you can directly put these formulas and directly get the answers and that will save time. So that will create an edge. Okay cool.

[00:32:22]Now [gasps] s relationship between marity percentage composition density and molar mass of solute. I hope you know the terms. What are these terms?

[00:32:32]Now let us begin the explanation. Sir, marity you have told us it is number of moles of solute upon volume of solution in liters. If I'm placing this volume in ml, then I need a,000 in the numerator. What next sir? Beta we know mass equals volume into density. So volume will be equal to mass of solution on density density of the solution. I'm putting in the numerator and writing it as small D. But because I have taken weight in gram and volume in liter that means this density has to be in g per ml or g per cc because 1 ml is nothing but 1 cc. I hope everybody is clear. Yes [clears throat] sir. Now sir but uh I need percentage.

[00:33:19]So let us let us now let us now write this formula again. So I can say marity is equal to now instead of number of moles of solute what you can write you can write weight of solute in gram upon molar mass of solute we already have weight of solution in gram and a density in the numerator and the th00and in the numerator. Now can you do you remember what is weight by weight percentage? Yes sir. Weight of solute upon weight of solution into 100. This green arrow is nothing but mass percent mass of solute. Mass of solution into 100. That means sir what are we left with? We are left with this density. We are left with this 10 rupees upon molar mass of solute. This is nothing but marity. I hope the formula is clear.

[00:34:18]Now you can obviously directly put in the values and by common sense also you can do but yes for advance I will definitely say even I do not ask my students to learn these formula because huh for means they have to so anyway for and neat you even have to I hope you are clear now again a important relationship sir density molar m marity marity molar mass of solute and this thousand how to derive sir Beta very important direct form direct questions are asked let us derive sir we know molarity is equal to now I'm I'm writing it number of moles of solute in 2000 why because volume of solution in ml but not writing volume also because mass equals volume into density so volume equals mass of solution upon density so I'm directly you coming till this moreover sir sir you know we also know this and we also know because we have to relate It's small m also which is mality. Mality is equal to number of moles of solute upon weight of solvent. If this is in gram then 1,000.

[00:35:25]Moreover sir mity if you write weight of solute as number of moles weight number of moles as weight of solute upon molar mass of solute sir into weight of solvent into th00and then this is also one of the form of mality. But what I am interested first is in beta look at this n_sub_2 [snorts] into look at this n_sub_2 into th00and.

[00:35:47]So in equation first can you replace n_sub_2 into th00and with this? Yes sir.

[00:35:52]That will do what sir that will at least relate capital m with small m. So capital m will be equal to instead of this bubble I'm writing mality into w1. So small m into w1 then I already have this d which is density of solution. Then sir in the numerator in the denominator you have weight of solution. What is solution sir? S solution is solute plus solvent. So solution will be weight of solvent plus weight of solute array. Sir we can see formula happening where how array beta can you see d? Yes sir, I can see D. So take D in one side. Okay sir, taken sir.

[00:36:41]Can you see capital M? Yes sir, I can see capital M. Okay, beta.

[00:36:46]Now do cross multiply sir because this is D.

[00:36:52]This is M everything that this side because everything that side. So sir W1 + W2 but I will have a denominator M into W1. So do that sir m into w1 sir m into w1 sir m into w1 array sir w1 w1 got cancelled that means I have one upon mality also now only one thing is left sir what is left this bubble sir just work on this bubble sir I guess this bubble is already visible w2 w2 mality mality will go Sir W1 W1 that means it will be M_sub_2 upon 1,000. So sir M_sub_2 upon,000 I hope everybody got it. I hope everybody got it. Very important derivations beta but very important common sense also. Now, now coming to two more derivations although I have seen less number of questions in neat examinations beta but advance started it means copied it and I am very sure next is neat that's why I make you derive and learn these derivations as well what sir mality related with mole fractions molality small m related with mole fractions A very basic common sense beta. Now you should remember it also.

[00:38:22]Mality is equal to X2 into,000 upon X1 M1 derived it surface. So mality is equal to number of moles of solute upon weight of solvent in kg. And if I try to write it in gram then I need a,000 in the numerator. Everybody know it. Why you have created a space sir? Because because if you just write weight then sir number of moles is equal to weight upon molar mass. So weight of solvent will be equal to moles of solvent into molar mass of solvent. I hope this is common sense of number of moles. But if you just why I have given a difference because now I'm dealing with it with mathematical tweaking. Sir, if I divide this by n_sub_1 + n_sub_2 and if I divide this also by n1 + n2 s mathematically it is making no difference because 2 upon 3.

[00:39:18]If you have 2 upon 3 then 2 upon 5 is also equal to 3 upon 5 is also 2x3. So that is upon 5 upon 5 I have done mathematically and how it has helped me.

[00:39:32]Sir this is nothing but x2.

[00:39:35]So this is nothing but x1 sir I can see the formula happening. So mality is equal to x2 into 1,000 upon x1 m1. I hope everybody is with me on this guys I need affirmation.

[00:39:53]Whoever is reading, give affirmation.

[00:39:57]By the time I'm pouring some coffee for me quick, quick, quick, quick, quick, quick.

[00:40:10]Hi, Par. Oh, Parimala is our student beta.

[00:40:18]Hello, Parimala.

[00:40:21]Cho sir u a e gasper what are you writing casper jaro no yadu g I can very well speak Hindi Punjabi B English but read the name of the channel sir read The name of the channel sir it's English that's why I have that level of compassion beta because there are many student sir my chat's not working sir no beta pimala they are no worries beta okay I'm sorry uh Casper I didn't know that beta I thought okay I'm sorry I'm sorry I didn't know I didn't know that so Arian thank you okay that means okay Okay. I didn't know. See academic I mean uh we in the in night at 11:10 also we are this is uh Adan Pradan you know in transaction of knowledge is happening. So you are giving me new words. So thank you cho moving forward beta. Now the throat has been given some coffee. Now now let us start again. I mean proceed continue is the word now beta next is uh marity relationship with s mararity now we can do this we can do it sir come on I will do it beta this is my job so I have to do it although most of you I know if you're reading it properly you will do the derivation now sir you have told us it is equal to number of but because this is marity sir so you have to put volume okay beta so volume of solution but sir instead of volume instead The volume mass equals volume into density.

[00:42:18]So volume equals mass of solution.

[00:42:23]Mass of solution. I hope I'm audible guys.

[00:42:26]Hello. Huh? I just I a few of my students were saying sir you you dance a lot while teaching. I don't have master keeps teaching for the whole day. So how he will he or she will take uh enjoyment. So why dance? And uh I I mean not practically but we students say so ch now sir volume is equal to mass equals volume into volume equal mass upon density. So that density will come in the numerator and uh mass of solution can be written as mass of solvent plus mass of solute and sir you have uh and you have recently yes yes yes yes also you'll have a th00and why because sir volume was in liter so if you have converted ml then you need a th00and so that is a problem once you do things one step all the time all step in one line then sometimes you but yes with practice you'll obviously get to know it sir Now sir uh the trend is the same how marity is equal to sir I have n_sub_2 okay I have d and I have 1,000 and in the denominator sir I have w1 so instead of w1 what can you write sir you have already told us before in terms of moles it is moles into molar mass of 1.

[00:43:48]So number of moles of 1 into molar mass of 1 plus number of moles of two into molar mass of two. Now again do that mathematical twinkle.

[00:43:57]n1 + n_sub_2 derides sir. N1 + n2 divides sir. N1 + n2 divides sir because mathematically no error sir. I hope you are seeing the formula.

[00:44:08]X2 into d into,000 upon x1 m1 plus x2 m2 beta. This is a clear-cut trend. In fact this question was started by J mains.

[00:44:21]The exact question the they even asked the formula only this formula only was asked a very probable one for neat as well moving forward. Yes. Yes.

[00:44:34]Now there are many questions beta but because we have done those derivations so now sir are you not going to solve these question for us? I will I am def definitely but beta I want you to practice first. Those derivations has given you some common sense. Now it will bid your confidence sir but if we will find problem the description section is always there. I hope everybody's clear.

[00:44:55]So a homework few homework questions for you. So again the relationships whatever. Now sir can you do advanced question also with just read the question directly formula will be will be helpful. So you have we have told us the derivation also. So you have not learned them. You have understood them.

[00:45:11]And yes once you do the derivation once beta the formula will definitely be in sync. you'll definitely learn the formula and yes I would rather suggest also that you should iterate a few more times so that you can keep it for a longer duration because it will help you and so again some homework questions beta I am [clears throat] giving you all these questions not writing homework okay let me write one homework moving forward now sir sir now concentration term done sir now let us go to collleative property yes came to collleative property but before entering collleative property we should first try to understand what is vapor pressure.

[00:45:49]Now once you have a liquid that then at any temperature t I am not talking of boiling. Let me revise boiling for you from class 11th. Boiling is the temperature at which vapor pressure of a liquid becomes equal to atmospheric pressure that can only take place at boiling point. I'm not talking of boiling. I'm talking of the surface phenomena of vapors present at the surface of a liquid always experience a net force and at temperature T they will have some kinetic energy because kinetic energy is proportional to absolute temperature. So every absolute temperature will give some kinetic energy to the surface molecules. The surface molecules will try to occupy the outside environment of the container. So initially sir this is what sir this is evaporation not boiling because evaporation is a surface phenomena only surface phenomena not a bulk phenomena.

[00:46:44]So initially just think of it like a uh physical equilibria where H2O liquid let's say this is H2O. So H2O liquid is transforming into H2O gas. That means you just have to think of this physical equilibria H2O liquid transforming to H2O gas. Okay sir.

[00:47:02]So at time t equal to0 you will be having all the reactant molecules physical reactant. So at initially rate of evaporation will be maximum just like rate of forward reaction and rate of backward reaction as in condensation will be zero. Yes sir. And once equilibrium will be reached at that particular temperature T any temperature T will have some pressure any. So at that particular temperature because equilibrium is only value of equilibrium constant only depends upon temperature.

[00:47:31]It do not depend upon the amount of of of reactant taken. Therefore at equilibrium once rate of evaporation becomes equal to rate of condensation as in liquid forward reaction becomes equal to backward reaction that means that initially there were no yellow balls gas after that yellow ball start increasing increasing increasing but as they start increasing condensation also started at equilibrium rate of evaporation became equal to rate of condensation and now it has been the concentration of these gases will become constant and this constant pressure of the vapors of this liquid at this particular temperature is called the vapor pressure of this liquid at this temperature. Hello.

[00:48:14]Hello. I hope you got it. Now you tell me if I have one liter water or 1,000 liter water it will it make a difference to the vapor pressure? No. Why? [gasps] If you have this equilibria happening, what is the value of equilibrium constant in terms of partial pressure?

[00:48:35]It is equal to partial pressure of hydrogen of water vapors raised to the power 1 because stoometry is one. And so pure solid pure liquid has negligible pressure. So we we assign in them as unity in the calculation of equilibrium constant K. That means sir the value of this pressure of the gaseous water vapor as in this is vapor pressure. This vapor pressure is equal to what? K. You know that value of K depends upon concentration. It depends upon No sir value do not depend upon the concentrations and pressure. Value of K is always a constant till temperature is a constant. I hope you're getting it.

[00:49:15]So that's why technically we even uh theoretically the vapor pressure of water is even termed as aquas tension.

[00:49:25]So aquest tension do not depend upon amount of water. Even I have one glass of water or a river full of water. The vapor pressure at constant temperature will always be constant. That means the humidity the aquas tension in all the area is same. Even you have a big tank of water in your place or somebody is living in the road outside you, you both will feel the same level of humidity.

[00:49:50]Yes, you can put your AC inside your room but outside it is same. So sir equention as in vapor pressure only depends upon only depends upon temperature. I hope you're getting it.

[00:50:03]That brings us to the conclusions for vapor pressure which is which is very important conclusions beta because statement based questions are also very famous these days. So first one is vapor pressure of pure liquid is only temperature dependent not on the amount of liquid irrespective of the amount of liquid and shape of container vapor pressure is always constant. Sir you have already told us but yes you have to know beaker size shape also doesn't matter. Now so liquid should be sufficient enough to make Yes. Yes. Yes.

[00:50:39]For example, I need some level of water vapor pressure that can be become equal to value of K. If I have very less water, then let's say all the water has vaporized but still the value of equibrium constant K has not been achieved then you then that pressure is not saturated. So what is vapor pressure? when the vapors are saturated.

[00:51:04]If the liquid is very minimum, then the saturated level has not even yet reached. So the equilibrium has not even established. So in that case obviously you can have more vapor pressure because at that particular pressure that is that has not even reached the value of saturated pressure. So that will be called an unsaturated uh mixture and during that time the vapor pressure will not be termed as saturated vapor pressure. It is unsaturated.

[00:51:30]Okay. Now last and the most important point vapor pressure depends on temperature.

[00:51:37]How? Exponentially. Sir, how do you know it? Because you know how equilibrium constant K changes with temperature. I hope you remember this formula. If not, please remember this. What? Log of K2 by K1 as in equilibrium constant at temperature 2 upon equilibrium constant at temperature 1 is equal to delta H upon 2.303 R 1 upon T1 - 1 upon TS2.

[00:51:59]Yes, we can d definitely derive this using vanto equation which is d by dt of ln k is equal to delta h upon rt². You can definitely derive it but I that we do for random equation we do in our advanced classes but this is the result sir. Why instead of k you have written p beta? I hope that you remember because k is nothing but partial pressure. So equilibrium constant and partial pressure R1 and the same thing. So P vapor pressure is related with temperature in an exponential form. It is not linear. It is linear for PV equal to NRT for gases. The the vapor pressure that are created by saturated liquid vapors. I mean the liquid has created those vapors saturated pressure. So that is not linearly changing with it increases with temperature but the increase is not exponent. The increase is not linear. It is rather exponential.

[00:53:00]I hope everybody's clear. Now sir, uh why do different liquids have different boiling points, sir? Because their attraction forces are different. Which is the strongest attraction force? There are many attraction forces through chemical bonding. But but but you should just know the basic intermolecular forces. What are they? The strongest one is hydrogen bonding. So if hydrogen bonding exist between two molecules then it is having strongest intermolecular forces. So boiling point will be high.

[00:53:33]Less than that will be s dipole dipole attraction uh this one and least will be s wonderall forces of attraction as in instantaneous dipole dipole attraction. So stronger be the force of attraction the the stronger the molecules are bounded with each other and higher will be their boiling point.

[00:53:52]I hope that is also clear. Now again sir this also serves gives us a question.

[00:53:58]Yes. Now read the question. The question says you have few liquids and you have to mark which of which one of them is incorrect. So let us do it. Now it says the now you have to mark the uh graph are given and you have to mark the correct inference. So statement A says X has higher intermolecular interactions as Y. Now just look at the graph sir.

[00:54:22]How can you compare intermolecular forces of attraction beta? What is boiling? Sir, boiling is the temperature. Boiling is the temperature at which vapor pressure becomes equal to atmospheric pressure. So let us assume what is atm somewhere around 760 mm of Hg. So let's say this is 760 mm of Hg.

[00:54:39]So now you tell me when the vapor pressure of X reaching 760 mm sir at this temperature. When Y is reaching that pressure sir at this temperature when zed is reaching reaching that temperature sir at this whose temperature is more s let's say this temperature is t_s_1 this is t_sub_2 and this is t3 that means sir zed is creating this much pressure at higher temperature that means the attraction force of zed will be highest or strongest that means of x will the least and that means a Y will be intermediate as in moderate between them. So read the statement now. X has higher intermolecular interaction. No sir, it has least. So this is wrong. X has lower intermolecular interaction as compared to Y. Yes, X has low. So it is correct.

[00:55:35]Zed has lower intermolecular. Zed. No sir, Zed has high. Yes. So you are also wrong. So only B is correct. Option one is right.

[00:55:44]only B is B statement is correct. So option one is right. I hope everybody got it guys guys.

[00:55:51]Perfect. Now once you know this now you can understand now you can understand collleative properties as well or how to understand collleative properties. Now you know vapor pressure. So you tell me now you know vapor pressure. So you tell me because you know what is vapor pressure. Now let us say I have pure liquid that pure liquid as in beta pure liquid as in you just have let's say water. Basic example let's say at temperature T I'm having some water vapors.

[00:56:32]I'm having some water vapors. Let's say the pressure of these water vapors which are saturated at this particular temperature T is the vapor pressure of pure solvent which is water. So representing them as P not okay sir.

[00:56:49]Now I am changing this solvent. I am making it a solution. How? But I am introducing a solid. Let's say I am putting some sand over here.

[00:57:03]And after putting this sand which is definitely a nonvolatile solid solute.

[00:57:09]Which is a nonvolatile solid solute.

[00:57:13]Which is a nonvolatile solid solute. Now you tell me at the same temperature T definitely some solvent molecules will go.

[00:57:22]But you tell me let's say this pressure is pressure of solution. You tell me this pressure of solution will be more or less. It will definitely be less by him. Why? Because sir, let's say at temperature t you were supplying 100 rupees of heat for example 100 rupees. All the 100 rupees taken by a liquid solvent and they are vaporizing evaporating not boiling at temperature I am again supplying 100 rupees but some of that 100 rupees this sand will also take and sand not sand will take heat will will get hot but no will it is nonvolatile so it will not produce any vapors so this guy has taken let's say 30 rupees so the liquid water will only take 20 100 100 was producing let's say 100 molecules so 70 will produce 70 because now this has taken 30 rupees and not giving any vapors out of it I hope you're getting it that means sir it is always true that whenever you add a nonvolatile solute in a volatile solvent volatile as in which vaporizes easily has less boiling point nonvolatile as in do not vaporize at that particular temperature that means has very high boiling point I hope that English is also clear. So then I can definitely say there will always be a lowering in what?

[00:58:48]In vapor pressure and that lowering will be mathematically solvent minus solution.

[00:58:55]If you take the fraction it will be termed as relative lowering of vapor pressure and what is with difference minus initial upon initial value. So P minus PS upon P is termed as relative lowering of vapor pressure. And I am saying and I am saying it is a collleative property and I am saying it is a collleative property. Yes sir. We do not even know what is collleative property and you are saying it is a collleative property. What the hell this mean?

[00:59:31]Now in order to prove and understand it is a collleative property, let us first understand Raul's law. Now what is Raul's law? This law states that partial vapor pressure of each component in a solution is proportional to its mole fraction in the solution. Sir, we didn't understand anything. I didn't tell you anything then sir. Why you have shown this? Because wait after I'll make you understand this. Uh again for your class 12 boards also the same statement is asked. One mark question state's law. So my job is to teach you for for mains also advance also neat also obviously we are in neat platform and for your class 12 boards as well you must have seen people scoring 90 and 99 percentile not getting 75% in B board that I do not know how to write whether God has not given you hands or what the only thing is you must keep on be vigilant beta be vigilant be vigilant know teachers responsibility so don't worry just join our batches everything will be done now sir you are promoting in between [clears throat] why I should not if we are doing such great job then why I should not promote I will and I am chal moving forward let me borrow some slides now now choo from here our job starts now let Let us be very precise after this. Yes, we have a lot of other methods in my batch in our batches. We do this in like uh 12 13 lectures. So if I'm doing it in a single lecture, then obviously I have to make the content precise. So let me start making precise from now. Now sir, we know what is RLVP but tell us why it is collleative and what the hell is this collleative property? So point is beta. The first and foremost point is what is rel what is this Raul's law? It has been statistically observed that if you have if you have a liquid component A and let's say I have another liquid component B.

[01:01:52]Then at temperature T, A was forming some vapors and B was also forming some vapors. We know it is P A and it will be P B as in vapor pressure of pure component A and B. Now let's say if I have converted both of them in a in a single bucket. So it will be a solution having A also having B also and I will be having pressure.

[01:02:21]So this will be pressure of solution.

[01:02:25]Dton's law tell us that pressure of solution will be partial pressure of A plus partial pressure of B here. So this is no maths. This is just basic Dton's law. Let's say number of moles of A is NA here and number of moles of B is NB here where I am talking of the liquid solution.

[01:02:46]But sir sum of the A and B will be in the vapor phase only because of those vapors only I'm having this total pressure of the solution. Let's say number of moles of A in vapor phase is NA dash and number of moles of total moles of B in vapor phase is NB dash.

[01:03:02]These are moles in gaseous phase.

[01:03:10]Sir Dton's law told us one more thing from class 11th. This total pressure is what part of this total pressure is created by a whatever a fra whatever moles of a in gaseous phase UV you have that will decide the fraction that means through dalton's law you know this also that partial pressure of a is nothing but total pressure as in pressure of solution into mole fraction of a in gaseous phase now what is y a is n a dash upon n a dash dash plus NB dash as in mole fraction of A in gaseous phase.

[01:03:50]Similarly, the partial pressure of B will be equal to total pressure into mole fraction of B in gaseous phase and it will be equal to NB dash upon NA -ash plus NB dash. So these are all the conclusions that we have through Dalton's law.

[01:04:13]You were supposed to tell us Raul's law.

[01:04:15]You are telling us common sense. Wait.

[01:04:19]Now Dalton is relating things practically. Rald did it experimentally and proved that you have pressure of a.

[01:04:30]Yes. So Raul told us now R A O U L T S R's law is that partial pressure of A over the solution is directly proportional to the mole fraction of A in the liquid phase. So the more you are you are present in the liquid phase you will have a more possibility of coming in the vapor phase and that's why you're producing that pressure.

[01:05:01]This is not common sense. This is what Raul has experimentally and statistically derived. So this becomes Route law which says partial pressure of A is also related with the amount of A present in the liquid solution. That means mole fraction of A in the liquid solution and in the liquid solution it is represented as X. So what is the proportionality constant? Because I'm saying it is a statistical law. Also the proportionality constant came out to be pure vapor pressure of A when it was alone. So P A into X A. And I hope you now know what is X A sir. X A will be equal to moles of A upon moles of A plus moles of B but in the liquid phase.

[01:05:51]I hope everybody is clear. I hope everybody is clear. Now sir that means partial pressure of B will also be PB into XB and sir we know X A plus XB is 1. Similarly Y A + YB is also one. So if you combine Rul and Dton's law you can calculate you can calculate pressure of solution.

[01:06:17]So pressure of solution will be P A into X A plus P B into XB. Yes, Shashi Taru's way of saying XA and XB, Sky A and Sky B. But GSA way is XA and XB. I like it keeping it simple.

[01:06:37]Sir, similarly PA is equal to P A into XA as per route law and it is equal to total pressure into Y A as in you can relate mole fraction of A in liquid and vapor phase. Similarly you can say for partial pressure of B it is equal to PB into KB it is also equal to PS into YB.

[01:06:58]So these are some conclusions and it was theoretically said that whatever solution which will follow this will be termed as will be termed as ideal solution as in if your actual vapor pressure is coming out as per calculated by route law then you are eligible to be called as an ideal solution.

[01:07:26]If not because practically what are ideal solution? There are no ideal gases. So there are no ideal students.

[01:07:32]So there are no ideal solution. But yes, what is more or less ideal? Like chlorobenzene, bromenzene, like hexane, heptine. So which have same property are more or less ideal. Point number one, what are non ideal solutions are where the pressure of the solution is not equal to this. So let me not let me not do it over here rather let us create another slide. So this is the another slide I have copied that thing down. So whenever the pressure is not equal to then those solutions are termed as non ideal solutions. These non ideal solutions are of two types. One showing positive deviation, one showing negative deviation.

[01:08:22]What are the solutions that show positive deviation from Raul's law? Sir, if you want to show positive deviation from Raul's law, then that definitely mean that whatever AA and BB interaction was there, AB interaction is weaker.

[01:08:37]That's why A and B are running away from each other. That's why they are creating more pressure.

[01:08:43]But give us an example. Beta whatever [snorts] whatever type of solutions you mix who have different type of intermolecular attraction like acetone is a polar molecule carbon dulfide is a non-polar molecule so they will run away from each other methile alcohol and ethile alcohol have relatively relative level of H bonding so water has very strong H bonding so they will also run away from each other So what are ideal solutions which are belonging to same functional group just homologous series like hexane, heptine, cyclopropane, cyclloututins so on and so forth. Although they are exactly not ideal they are more or less side. What are non ideal? What is pos non ideal?

[01:09:32]positive deviation. So when they they have different category of intermolecular forces and how you can have negative deviation s negative deviation you can only have negative deviation you can only have when solvent A and solvent B are having some special attraction force and that special attraction force is always H bonding. So like chloroform sir we know chloroform it's CH3 which will make this hydrogen because carbon has turned electrogative because of three chlorine so it will also withdraw electron so this hydrogen will attain delta positivity very high acetone sir we know that acetone is a highly polar molecule because of the carbonile group so this oxygen will be having sufficient minus charge and this minus plus will attract each other and this extra force of attraction is called H bonding which will bring them close that's why they will show less pressure.

[01:10:32]So whenever the total pressure the actual pressure of solution is less than the calculated value it is negative deviation whenever otherwise it is positive deviation. I hope you can you know that now sir why you are telling us this because now with this we are going to prove now this with this we are going to prove that RLVP is a collleative property. How sir? You have came some to some other area and now you are saying that you will prove. Yes, I will definitely prove. Let me help you with it.

[01:11:04]Now as I said Now as I said that pressure of solution is equal to P A into X A plus P B into XB. And while discussing P RLVP I have taken B as a nonvolatile solid solute. So if B is a nonvolatile solid solute that means PB is zero because in pure state that solid will not give any pressure. So for solid in liquid solution for liquid and liquid solution we have derived ideal solution.

[01:11:49]For solid in liquid solution this PB will always be zero. That means sir this pressure PS will be equal to P A into X A this factor is gone sir. Instead of X A if I write 1 - XB then you can definitely see write P A as P because this is just the solvent. So it will be P minus PS upon P which will be equal to mole fraction of solute which is equal to number of moles of solute upon number of moles of solvent plus number of moles of solute because why I'm writing two because now B is my solute and for solute I write two. I hope everybody is clear. Now what is a collleative property? All the properties which only depend upon which only depend upon the amount of solute with respect to solution or rather with respect to solvent and do not depend upon the nature of solute. They only depend upon the amount of solute. Those properties are called collleative properties. And because this is RLVP which is relative lowering of vapor pressure and it is depending upon solute with respect to solution. Hence it is also a [sighs] collleative property. Hence it is also a collleative property. Now sir collleative properties that means they are only valid for beta properties are only valid for those solutions.

[01:13:18]Colative properties are only valid for those solutions which have nonvolatile solid solute and it is valid for only those solutions which are highly dilute where amount of solute is very very very less than solvent. I hope everybody's clear where amount of solute is very very very less than solvent. Now sir do we have some other collleative properties as well? Yes. So first one is RLVP.

[01:13:50]Second and third are just the same. Sir why they are just the same? Because beta if you just do the common sense that for example for example I have this bucket I was having liquid in it.

[01:14:08]Now let's say I was let's say this is water. So what is boiling point of water? Boiling point of water is 100°C.

[01:14:17]boiling point of water is 100°C. Okay, that means for example, that means if I give this water 100 rupees of heat, it will boil. For example, if I again add a nonvatile solid solute, then again I'm supplying 100 rupees, but out of that 100 rupees, it will take 30 and it will not give any pressure. But this guy only got 30 rupees, 70 rupees.

[01:14:44]Initially it needed 100 to have vapor pressure equal to atmospheric pressure that is boiling. But now out I'm giving 100 rupees and out of that 100 rupees it is taking 30 and it is taking 70. So vapor pressure will be created by 70. So it'll ask for more 30 rupees. That means you have to increase the boiling point.

[01:15:03]That's why once you add a solid in a liquid boiling points get elevated and that is called elevation in boiling point written as delta TB which is boiling point of solution minus boiling point of solvent.

[01:15:16]Once you talk of depression in freezing point now again do the reverse thing.

[01:15:21]What sir? Do not see this solid. Now take 100 rupees this liquid will become ice.

[01:15:30]again add non-volatile solid solute sand again take 100 rupees this sand will also give heat let's say 30 rupees it is giving so 30 rupees I'm taking from him I need to take 100 rupees from this liquid then only 100 rupees of heat is taken and then it'll turn liquid uh it'll turn ice but now I have only taken 70 so this water will want take more 30 then I will freeze otherwise I'll not so I have to take out more heat that means I have to keep the freezer to even lesser temperature that means freezing point gets depressed that means freezing point get depressed as in boiling point is elevated but freezing point is depressed that means solvent will have high high freezing point and solution will have less so it will be delta TF not minus TF so not represents of the solvent not represents of the solvent and normal represents of the solution. So this is elevation in both sir. Why are they collleative? Why are they collleative?

[01:16:39]Because once we have done experiment on them, we again found that they were also proportional. Elevation in depression in boiling and freezing point respectively were increasing as amount of solute was increasing. What was the concentration term again? Now it is a statistical law that this was proportional to mality and this was also proportional to mality.

[01:17:02]Sir why you are not writing proportionality and because obviously it they are statistical. So proportionality constant was calculated. In this case proportionality constant is termed as KB and in this case it is termed as KF. KB is eloscopic constant. KF is cryoscopic constant. These are characteristic of solvent. So as solvent change they change otherwise they do not change.

[01:17:24]That means that you can calculate them as well. Yes, you can definitely do it.

[01:17:29]KB will be equal to there is a trend to learn it. Remote as in RMT. Remote as in RMT. R as in universal gas constant. M as in molar mass of solvent because KB and KF are are characteristic of solvent. P is the boiling point of solvent. And if you are calculating KF it will be TF of boiling of freezing point of solvent upon 1,000 * of delta H in boiling it is delta H vaporization in in freezing it is delta H fusion. Hello. Hello. So many times this value of KB and KF is thrown at you in the questions. That is how you can make your questions correct. Okay sir. So because delta TB and delta TF both depends upon amount of solute there therefore they are also collleative properties. So how many collleative property now you know RLVP delta TB delta TF. Now there is one more collleative property. The last collleative property is osmotic pressure.

[01:18:36]Now for knowing OS for understanding osmotic pressure you first need to know what is osmosis.

[01:18:43]You first need to know what is osmosis.

[01:18:45]So let's say I have a height full of solution that means I have over here let's say I have solute also and I have solvent also but the similar height I'm having of only solvent and here I have a semi-permeable membrane. What is it? It is like a seieve a chney by which you you you pass your chai so that the tea flows through it but the but the tea leaf the chai pati gets stuck in the seieve in the filter. So that the semi-p permeable membrane is just like that filter. So through the small size of those filter only small particles as in solvent will move solid solute will not move. So it will only allow flow of solvent. Okay. Anything flow from where?

[01:19:36]From high concentration to lower concentration. If the height is same where solvent is more so there solvent is more here solvent is less. So solvent will move move from higher concentration towards lower concentration through a semi-p permim membrane. If it start happening then the pre then the height will increase. I do not want it to increase. Then I will apply some extra pressure. That extra pressure is represented as pi. And this pressure is called osmotic pressure. So what is osmotic pressure? the pressure applied on the solution side to stop the flow of solvent from solvent side to the solution side and this process is called osmosis. So the process the pressure applied to stop osmosis is called osmotic pressure. If you just apply a slightly more pressure than the osmotic pressure then solvent will move from this side to that side that means bad water tap water impure water will be purified. So reverse osmosis R O. So this is the the principle the guiding principle of the machine that you have in your place. So now we know what is osmotic pressure. But tell me why it is collative. Again calculations done and it was found that the osmotic pressure pi was also proportional to number of moles of solute with respect to solution. What was the concentration term? It was marity but here it is written as C. The proportionality constant was again r nt. So the formula becomes pi is equal to crt. C is marity.

[01:21:05]R is universal gas constant. T is temperature in kelvin. So this makes osmotic pressure also a collleative property. Now there was a problem. What sir? You said collleative property only depends upon the amount of solute as in number of solute. They do not depend upon the nature. But sir there are solute which ionizes in water.

[01:21:32]What about them? Because if I add 100 molecules of NaCCl the solution will be having 100 moles of Na plus also 100 moles of Cl minus and also. So collleative property will think there are 200 people but we theoretically we will we thought we had only 100. So what about those case of dissociation and association and because of that many of the problems were fa faced by the scientific community. Because these qualative property calculation we employ for molar mass determination of organic macroscopic molecules your biomolelecules because biomolelecules are very large and all the collleative properties are proportional to number of moles of solute. Number of moles of solute is weight upon molar mass of solute. So if you fix the weight of solute then it is inversely proportional to molar mass. So all collleative properties inversely proportional to mar mass of solute and if collleative property value is getting changed then mar mass will change. So you get abnormal molar masses. So these the the community was was blown that a scientist came into existence. He was ter he was called he was called he was called Vanth and he gave a correction factor known as Vanth factor known as Vanth factor. And what Vanth said that I can correct all the collleative properties. How? He said you just do the ratio of the actual value of collleative property because actual value people were finding abnormality.

[01:23:05]So it is also called abnormal collleative property or experimental value of collleative property upon the collleative property that you know theoretically and whatever you know theoretically it is normal for you.

[01:23:24]And obviously we know collleative properties inversely proportional to molar mass. So the I can also be calculated as experimental molar mass or abnormal molar mass upon normal molar mass or theoretical molar mass of what?

[01:23:38]Of solute.

[01:23:40]So this is your correction factor. That means sir all the formula will be corrected. Yes. So the formula of corrected collleative property will be s relative loing of vapor pressure was P minus PS upon P. So it will it was equal to N_sub_2 upon N1 + N_sub_2. But now we know number of moles of solute has to be corrected by the factor of I. So I will be multiplied.

[01:24:09]Similarly, elevation in boiling point and depression in freezing point and osmotic pressure. The sir this is the actual value. So actual upon upon theoretical what is the theoretical formula? So delta TB is equal to KB into marity. But that will be corrected by I.

[01:24:28]So it will become I into KB into marity.

[01:24:32]It will become I into KF into marity. It will become I into CRT. Now sir let us calculate I finally so I in case of dissociating species is nothing but it is equal to 1 + n -1 * of alpha like for example if I have na so what will be the value of n_sub_2 because na plus minus if I have al3 so value of n will be four because 3/ minus and 1 na plus in case of al2 so4 whole thrice is two of these and three of these as in n will be five. I hope you're getting it. Sir, what about alpha degree of dissociation? Generally for strong electrolytes for ionic compounds this alpha is one. So sir alpha is one.

[01:25:21]So one one gone that means n will be equal to i. But yes for general it is this s sometimes some molecules only there is case of association I mean association of only one type of molecule. Yes, others can also take place but in general we just have to know the association of caroxilic acids.

[01:25:41]Why? Because you know they are associated with you know they are associated with hydrogen bonding and because of that hydrogen bonding two molecules exist together so they drize.

[01:26:00]So for them I will be 1 + 1 upon n -1 * of beta and this n will be 2 in case of dimer formation. Obviously it will be three in case of primer formation. I hope everybody's clear. Hello hello hello.

[01:26:20]I hope everybody's clear with this now sir. Sir after vent correction sir but you have to give us question sir. beta I you can obviously see I'm sliding so many uh slides that means obviously once you get these lecture notes you'll be getting loads of question to practice but yes do the theory and then directly do the pyq's beta it will be helping you like anything piq's what piq's of j means need because obviously you're need aspirant so do need first I hope everybody is perfect guys now last topic for your solution chapter is yes See they are all the questions sir one type of solution you left which one s liquid and solid done liquid and liquid done I mean sorry solid and liquid done liquid and liquid done one is left sir gas and liquid so solubility of gas and liquid that's is a common sense how let's say I have this coldering bottle you all know this coldering bottle is filled not till the brim why because if you need the liquid to have fizz that means I want CO2 gas inside it. This gas can only exist in the liquid once you have pressure of the gas of the same gas over the liquid solution.

[01:27:39]This is governed by Henry's law which is nothing but an extension of of of Ral's law that we have seen that is partial pressure of this gas as in CO2 over the solution will be equal to the amount of that gas dissolved. What is concentration term which Henry has used is the mole fraction of gas. But because I'm writing X, so the mole fraction of gas is in liquid phase. So mole fraction of gas will be number of moles of gas upon number of moles of gas plus number of moles of water. Obviously number of moles of gas is negligible in present in comparison to so denominator can be assumed to be number of moles of water also. Most of the time the calculations this will help to ease the calculation.

[01:28:23]Sir, what about proportionality constant? For Raul's law, it was P A.

[01:28:27]For for Henry's law, it is KH. And obviously, KH will be a property of the gas. So, if you want to compare gases, take their pressure same. So, the gas which is more soluble will have less value of K. The gas which is less soluble will have more value of K.

[01:28:46]I hope you're getting it. And similarly you will be getting so many and loads of question regarding Henry's law which also have some application that aquatic life is possible. Why you have oxygen in the water which is making aquatic life possible? Because oxygen has a partial pressure up upside whenever you go up the hill you get the uh because you have gone up. So pressure of oxygen is down because you have came above the atmosphere. So partial pressure of oxygen reduce so less oxygen will be dissolved in your blood vessels. So you will be feeling that anoxia and those those uh uh dizziness.

[01:29:23]Similarly if you go deep down the sea then the pressure will increase. So so your blood will have more of air. Air has more nitrogen. So more nitrogen will be dissolved in your blood. Once you come out the gas will blow out of your body. the nitrogen ones move out with high pressure create bends in your blood vessels. So that is also very fatal medical condition. So these are all some I mean yes biological impacts of of of these uh Henry's law and so I guess we are done with the general theory discussion today but yes I'm definitely telling you you will be requiring so many questions to practice to to streamline your study for the chapter of solution and collleate properties and how you can streamline attempt the pyqs how to attempt first read the theory write the theory sir from where to write get the lecture notes from PW neat English WhatsApp channel. Whatever doubts you'll be having just hit the comment section. Whenever I'll be coming with the next backlog discussion, I'll be discussing it soon. Okay. So, this is it from uh Goros Singhura. This is me signing off with loads of homework and responsibility to you that you will be doing your job to the best of your efficiency. With that, good night.

[01:30:41]Goodbye. I will see you soon in the next class. mobile.